How about moving sStatusStrings array into Flash? Save 12 bytes of RAM!

[brewmanz]

It's possible to save 12 bytes of static RAM by moving sStatusStrings array into Flash.
HelloCoroutine.ino (Nano, with extra CoroutineScheduler::list(Serial); in printHelloWorld)
Initial Memory : 2820 Flash, 240 Global
Making changes to Coroutine.h

    void statusPrintTo(Print& printer) {
      printer.print((__FlashStringHelper*)pgm_read_word(&sStatusStrings[mStatus])); // add pgm_read_word etc
    }

Making changes to Coroutine.cpp

const __FlashStringHelper* const sStatusStrings[] PROGMEM = { // add PROGMEM

Flash memory: 2820 Flash, 228 Global
A saving of 12 whole bytes!

(PS Some other irrelevant local changes made for Serial baudrate etc, should Flash not exactly match official version)

[bxparks]

If I remember my thinking on this, the sStatusString[] is used only by CoroutineScheduler::list(). If the list() function is not called in a program, the linker will optimize away the unused sStatusString[] so the PROGMEM will make no difference. The list() function is meant only for debugging, not for production. But even for debugging, I never found it as useful as I thought it would be. With some of the recent changes to reduce the flash size of a Coroutine, the name of the coroutine is no longer stored (to save flash memory), so the list() function is even less useful. Coupled with the fact that on AVR processors with limited flash, I recommend not using the CoroutineScheduler to save flash memory, and instead calling Coroutine::runCoroutine() directly in the global loop() function.

So putting it all together, I didn't feel like the 10-14 bytes of savings was worth the hassle. Maybe if I feel motivated before the next release, I might look into this. I have to regenerate the entire suite of benchmarks (AutoBenchmark and MemoryBenchmark), which is not hard, but time consuming, even with all the automated scripting infrastructure that I have built myself. So I'm probably not going to do all the work, just for this.

[bxparks]

FYI, I moved the sStatusString[] array to PROGMEM, since I am about to push a release. Saves 12 bytes RAM (ignore the "14 bytes" in the commit message, I obviously can't count).

[brewmanz]

If it's just for Debug, and you want to save even more space ... use self-defining data!
One enum and const data techniques I use is to make it a number that is also a char (or C-string is another technique)
For example:

    static const Status kStatusSuspended = 'S'; // was 0;

    /** Coroutine returned using the COROUTINE_YIELD() statement. */
    static const Status kStatusYielding = 'Y'; // was 1;

    /** Coroutine returned using the COROUTINE_DELAY() statement. */
    static const Status kStatusDelaying = 'D'; // was 2;

    /** Coroutine is currenly running. True only within the coroutine itself. */
    static const Status kStatusRunning = 'R'; // was 3;

    /** Coroutine executed the COROUTINE_END() statement. */
    static const Status kStatusEnding = 'E'; // was 4;

    /** Coroutine has ended and no longer in the scheduler queue. */
    static const Status kStatusTerminated = 'T'; // was 5;

and write with

      printer.print((char)mStatus);

And the C-String (only up to 3 printable chars, and better suited where RAM is not an issue)

    typedef uint32_t Status;

    static const Status kStatusSuspended = 'S' + 'u'*0x100 + 's'*0x10000; // was 0;

    /** Coroutine returned using the COROUTINE_YIELD() statement. */
    static const Status kStatusYielding = 'Y' + 'l'*0x100 + 'd'*0x10000; // was 1;

    /** Coroutine returned using the COROUTINE_DELAY() statement. */
    static const Status kStatusDelaying = 'D' + 'l'*0x100 + 'y'*0x10000; // was 2;

    /** Coroutine is currenly running. True only within the coroutine itself. */
    static const Status kStatusRunning = 'R' + 'u'*0x100 + 'n'*0x10000; // was 3;

    /** Coroutine executed the COROUTINE_END() statement. */
    static const Status kStatusEnding = 'E' + 'n'*0x100 + 'd'*0x10000; // was 4;

    /** Coroutine has ended and no longer in the scheduler queue. */
    static const Status kStatusTerminated = 'T' + 'r'*0x100 + 'm*0x10000'; // was 5;

and write with

      printer.print((const char*)&mStatus);

(You can probably guess that I am an Assembler programmer at heart)

[bxparks]

Ha, interesting idea on the encoding into uint32_t. I've done things like that for magic number in file formats. But for this? Umm, no. It actually wouldn't be so bad with the help of some CPP macros, but it's not worth the extra complexity just for this.